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Although nitrogen makes up three-fourths of the Earth's atmosphere, humans usually can't have fun with it unless it's compressed and cooled into a liquid.

Among the hundreds of uses of liquid nitrogen, one of the most popular is making instant ice cream -- an annual event at Colorado College that took place last week.

"When you pour it into the cream, it becomes gaseous nitrogen," said Kristine Lang (pictured above), an assistant physics professor at the college. "It basically just goes in the air and it leaves its coldness behind."

From a ladle, the compressed gas slowly was poured over bowls of cream and various toppings. Collegians and visiting middle school students eagerly stirred the congealing results. "If you put it in too fast," Lang said, "it just freezes into a big solid chunk."

The silvery liquid that spilled with every pour rolled across the table in small beads and felt shivery against the skin. "It doesn't hurt as long as it doesn't pool in your hands," she advised.

"It's good," said CC senior Anne Roller, a biology major who recently used liquid nitrogen in class to freeze mushrooms in order to purify an enzyme they contained. "It's a little bumpy, but I guess I didn't stir it enough."

Lang also placed a peeled banana and a red-and-white rose into the Styrofoam cooler filled with compressed gas. She then proceeded to smash them.

Although the chemistry department should have rights to put on the annual social, Lang said the physics department beat the beaker-heads to the punch.

"We claimed it," she said, satisfied with another year's demonstration.